Multistimuli responsive ternary polyampholytes: Formation and crosslinking of coacervates

A series of multiresponsive ternary polyampholytes were prepared by free‐radical copolymerization of N‐(3‐aminopropyl) methacrylamide hydrochloride (APM), methacrylic acid (MAA), and N‐(2‐hydroxyethyl) acrylamide (HEA). APM and MAA were held at 1:1 molar ratio, while the HEA monomer feed was varied between 14 and 33 mol %. Compositional drift during polymerization was monitored by ¹H nuclear magnetic resonance, and minimized by adjusting the reactivity of MAA through its degree of ionization. The resulting polyampholytes phase‐separate from aqueous solution to form coacervate droplets, depending on HEA content, pH, ionic strength, and temperature. These coacervate droplets could be covalently crosslinked and the resulting hydrogel particles were found to swell with increasing ionic strength. Such soluble and microgel polyampholytes open opportunities for new multistimuli responsive biomaterials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2109–2118     

Effects of pH,salt, surfactant and composition on phase transition of poly(NIPAm/MAA) nanoparticles

The volume phase transition of poly(NIPAm/MAA) copolymer nanoparticles in buffer solutions at various pH and in aqueous solutions of KCl or ionic surfactants (SDS and DTMAB) was systematically studied using dynamic laser scattering technique. It was found that ionizable MAA groups imparted a responsiveness of the particles to pH and electrolytes. At pH > pKa of the copolymer, electrostatic repulsion of negative charges, mostly from COO⁻ groups, was a governing mechanism for preventing the particles from collapse at T > T_tr. The particles exhibited a sharp volume phase transition upon elimination of the negative charges by decreasing the pH of the medium or by the addition of cationic surfactant. At pH < pKa, the presence of MAA groups enhanced the hydrophobicity of the particles as indicated by a lower T_tr and a sharper volume phase transition. A pH 4 buffer at the same ionic strength exhibited the most significant effect on the particle size and phase transition, followed by the ionic surfactant with an opposite charge (e.g., DTMAB), KCl, and finally the ionic surfactant with the same charge (e.g. SDS). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2667–2676, 1999     

Synthesis and self‐assembly of thymine‐ and adenine‐containing homopolymers and diblock copolymers

Atom transfer radical polymerizations (ATRPs) of 1‐(4‐methacryloyloxy‐benzyl)thymine (MAT) and 9‐(2‐methacryloyloxyethyl)adenine (MAA) were conducted for the synthesis of DNA‐base functionalized polymers. The association equilibrium constant K_asso between MAT and MAA and the complexation equilibrium constant K_comp between the corresponding polymers PMAT and PMAA were determined. A zipper‐like diblock copolymer, PMAT‐b‐PMAA, was prepared by anchoring the PMAT and PMAA blocks on the ortho‐positions of a pyridine ring via a successive two‐step ATRP. Dynamic light scattering and atom force microscopy confirmed that the block copolymer had a V‐shaped configuration in dimethylsulfoxide/N,N‐dimethylformamide. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5995–6006, 2006     

Anionic amphiphilic end‐linked conetworks by the combination of quasiliving carbocationic and group transfer polymerizations

A series of amphiphilic end‐linked conetworks was synthesized by the combination of two “quasiliving” polymerization techniques, quasiliving carbocationic (QLCCP) and group transfer polymerizations (GTP). The hydrophobic monomer was polyisobutylene methacrylate synthesized by the QLCCP of isobutylene and subsequent terminal modification reactions. The hydrophilic monomer was methacrylic acid (MAA) introduced via the polymerization of 2‐tetrahydropyranyl methacrylate followed by acid hydrolysis after (co)network formation. The conetwork syntheses were performed by sequential monomer/crosslinker additions under GTP conditions. All the precursors and the extractables from the conetworks were characterized by gel permeation chromatography and ¹H NMR. The resulting polymer conetworks were investigated in terms of their degree of swelling (DS) in aqueous media and in tetrahydrofuran (THF) over the whole range of ionization of the MAA units and in n‐hexane for uncharged conetworks. The DSs in water increased with the degree of ionization (DI) of the MAA units and the hydrophilic content in the conetwork, whereas the DSs in THF increased with the reduction of the DI of the MAA units. The effective pK of the MAA units in the conetworks increased from 8.4 to 10.5 with decreasing MAA content. These findings can facilitate the design of similar unique conetworks with adjustable swelling behavior and composition‐dependent pK values. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4289–4301, 2009     

Synthesis and characteristics of poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three‐step reaction. The first step was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA‐NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA‐NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5203–5214     

Ionization equilibrium in salt‐containing aqueous solutions of synthetic polyampholytes

The peculiarities of ionic equilibrium in salt‐containing aqueous solutions of polyampholytes (acrylic acid–2‐methyl‐5‐vinylpyridine copolymers) of various compositions and molecular weights were studied. The protonation degree of base groups (β_iep), the dissociation degree of acid groups (α_iep), and the ionization constant of methylvinylpyridine groups (pK_b) for the isoelectric points of the studied polyampholytes under various ionic strength values (I) were assessed spectrophotometrically. The dependencies of α_iep and pK_b versus the copolymer composition in the absence of low molecular weight electrolyte are described by the following equations: pK_b = 6.2–0.037z and lg α_iep = 0.27–0.0215z, where z is the molar content of the acrylic acid units. The basicity of methylvinylpyridine groups increases in proportion to the content of acid groups at a constant ionic strength and is independent of the molecular weight and molecular weight distribution of the copolymer. The relationship between pK_b and the ionic strength of the solution for acrylic acid–methylvinylpyridine copolymers was established: pK_b(I) = pK + B · I^1/2, where pK is the thermodynamic ionization constant of base groups and B is 0.21 + 0.0065z. A good agreement between the experimental and theoretical (calculated from the given equation) values of the ionization constant, pK_b, of methylvinylpyridine groups for other polyampholytes (copolymers of methacrylic acid with 2‐methyl‐5‐vinylpyridine) demonstrated that the ionic state of polyampholytes is determined by the basicity of methylvinylpyridine groups, which depends on the copolymer composition and solution ionic strength. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1824–1831, 2000     

Synthesis,Characterization and Aqueous Solution Behavior of a pH-responsive Double Hydrophilic Block Copolymer

The pH-responsive double hydrophilic block copolymer poly(ethylene glycol)-b-poly(methacylic acid-co-4-vinyl benzylamine hydrochloride salt) (PEG-b-PMAA/PVBAHS) was synthesized. A series of PEG-b-PMAA/PVBAHS with different molecule weights and compositions were characterized by IR, ¹H-NMR, elemental analysis and TGA. With different MAA/VBAHS ratio, the PEG-b-PMAA/PVBAHS copolymers had the different isoelectric point (IEP). Supermolecular structures of the block copolymers could be formed by the interionic interactions at different solution pH. Experiment results showed that the structures of the pH-responsive copolymers in aqueous solution could be changed at different pH environments. The aggregation of this double hydrophilic block copolymer in aqueous solution was determined by both of solution pH and copolymer composition.     

Synthesis of anionic amphiphilic carbosilane block copolymer: Poly(1,1‐diethylsilacyclobutane‐block‐methacrylic acid)

An amphiphilic block copolymer of silacyclobutane and methacrylic acid (MAA) was synthesized via a living anionic polymerization of 1,1‐diethylsilacylcobutane (EtSB). Sequential addition of 1,1‐diphenylethylene and t‐butyl methacrylate (tBMA) to living poly(EtSB) in the presence of lithium chloride gave poly(EtSB‐block‐tBMA) with narrow molecular weight distributions. The t‐butyl ester groups in the obtained polymer were readily hydrolyzed via heating in 1,4‐dioxane in the presence of concentrated aqueous hydrochloric acid. The block copolymer with a short MAA segment was soluble in chloroform and insoluble in methanol and basic water, whereas the block copolymer with a long MAA segment was soluble in methanol and basic water and insoluble in chloroform. The block polymer (EtSB/tBMA = 45/60) formed a monolayer film on the water surface; this was confirmed by surface pressure measurement. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 86–92, 2001     

Amphiphilic conetworks. IV. Poly(methacrylic acid)‐l‐polyisobutylene and poly(acrylic acid)‐l‐polyisobutylene based hydrogels prepared by two‐step polymer procedure. New pH responsive conetworks

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(methacrylic acid) (PMAA) or poly(acrylic acid) (PAA) and hydrophobic polyisobutylene (PIB) chains. These conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB–IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four methacrylic groups per chain, was copolymerized with methacrylic acid (MAA) or acrylic acid (AA) by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 31–79 mol % of MAA or 26–36 mol % of AA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proven by swelling in both aqueous media with low and high pH and n‐heptane. The effect of varying pH on the swelling behavior of the synthesized conetworks is presented. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1284–1291, 2009     

Thermosensitive and redox-active polymers: Preparation and properties of poly(N-ethylacrylamide-co-vinylferrocene) and poly(N,N-diethylacrylamide-co-vinylferrocene)

Thermosensitive and redox-active polymers were prepared by copolymerization of N-ethyl- or N,N-diethylacrylamides with vinylferrocene (VFc). LCST (lower critical solution temperature) of the aqueous copolymer solution was decreased by increasing the ferrocene content in the copolymer. The oxidation of ferrocene led to a significant increase in LCST due to the transition from hydrophobic to hydrophilic character of the ferrocene moiety in the copolymer. The ferrocene content in the copolymer increases with increasing differences between the LCST's of the oxidation and reduction states. The transition could be made reversible by redox reaction using L -ascorbic acid as an oxidant and cerium sulfate as a reductant. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1967–1972, 1997     

Synthesis of 3‐(tert‐Butoxycarbonylmethyl)‐N‐vinyl‐2‐caprolactam and Homologous Copolymerization Toward Biocompatible Carboxylated Poly(N‐vinyl‐2‐caprolactam) Responsive to pH and Temperature

A new monomer derivative of N‐vinyl‐2‐caprolactam (VCL), namely 3‐(tert‐butoxycarbonylmethyl)‐N‐vinyl‐2‐caprolactam (TBMVCL), was synthesized via nucleophilic substitution at the α‐carbon to the lactam carbonyl group. The monomer was copolymerized radically with VCL and the copolymer compositions were controlled through varying the molar feeding percentages of TBMVCL. The resulting copolymers exhibited temperature‐responsive properties in water, with cloud points decreasing from 33 °C to 13 °C when the TBMVCL composition increased from 2.2 mol % to 18.6 mol %. Removal of the tert‐butyl protecting groups via acid hydrolysis exposed the carboxyl groups, which conferred pH sensitivity to the thermoresponsive properties of the resulting deprotected copolymers. The cloud point was found to increase with the increase of solution pH from 2.0 to 7.4, due to the ionization of the carboxyl groups. The influence of pH was most drastic for the 18.6 mol % copolymer composition. Furthermore, the phase transition temperature of the deprotected copolymers was found to be dependent on the polymer solution concentration, exemplifying classical Flory–Huggins miscibility behavior. Comparison of responsiveness was also made with another type of carboxyl functionalized poly(N‐vinyl‐2‐caprolactam) copolymer reported in our prior study, to examine the influence of the chemical structure of the carboxyl substitution group. Finally, the deprotected copolymer was demonstrated to be biocompatible using a fibroblast cell culture. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 112–120     

Libraries of methacrylic acid and oligo(ethylene glycol) methacrylate copolymers with LCST behavior

Homopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO₂MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₄₇₅ and OEGMA₁₁₀₀) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA₂₄₆) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA₁₁₀₀ did not show any cloud point (CP) in the range of 0–100 °C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 °C for p(MEO₂MA), p(OEGMA₄₇₅) and p(OEGEMA₂₄₆), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA₄₇₅ and OEGMA₁₁₀₀ were prepared. The cloud points of the random copolymers of MAA and OEGMA₄₇₅ were found to be in the range of 20–90 °C; surprisingly, even though the homopolymers of MAA and OEGMA₁₁₀₀ did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA₁₁₀₀) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22–98 °C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138–7147, 2008     

Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3441–3451     

Synthesis of poly(p‐phenylene)‐poly(4‐diphenylaminostyrene) bipolar block copolymers with a well‐controlled and defined polymer chain structure

A poly(p‐phenylene) (PPP)‐poly(4‐diphenylaminostyrene) (PDAS) bipolar block copolymer was synthesized for the first time. A prerequisite prepolymer, poly(1,3‐cyclohexadiene) (PCHD)‐PDAS binary block copolymer, in which the PCHD block consisted solely of 1,4‐cyclohexadiene (1,4‐CHD) units, was synthesized by living anionic block copolymerization of 1,3‐cyclohexadiene and 4‐diphenylaminostyrene. To obtain the PPP‐PDAS bipolar block copolymer, the dehydrogenation of this prepolymer with quinones was examined, and tetrachloro‐1,2‐(o)‐benzoquinone was found to be an appropriate dehydrogenation reagent. This dehydrogenation reaction was remarkably accelerated by ultrasonic irradiation, effectively yielding the target PPP‐PDAS bipolar block copolymer. The hole and electron drift mobilities for PPP‐PDAS bipolar block copolymer were both on the order of 10^?3 to 10^?4 cm²/V·s, with a negative slope when plotted against the square root of the applied field. Therefore, this bipolar block copolymer was found to act as a bipolar semi‐conducting copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characteristics of poly(N‐isopropylacrylamide‐co‐methacrylic acid)/Fe3O4/poly(N‐isopropylacrylamide‐co‐methacrylic acid) two‐shell thermosensitive magnetic composite hollow latex particles

In this study, the poly(N‐isopropylacrylamide‐methylacrylate acid)/Fe₃O₄/poly(N‐isopropylacrylamide‐methylacrylate acid) (poly(NIPAAm‐MAA)/Fe₃O₄/poly(NIPAAm‐MAA)) two‐shell magnetic composite hollow latex particles were synthesized by four steps. The poly(methyl methacrylate‐co‐methylacrylate acid) (poly(MMA‐MAA)) copolymer latex particles were synthesized first. Then, the second step was to polymerize NIPAAm, MAA, and crosslinking agent in the presence of poly(MMA‐MAA) latex particles to form the linear poly(MMA‐MAA)/crosslinking poly(NIPAAm‐MAA) core–shell latex particles. Then, the core–shell latex particles were heated in the presence of NH₄OH to dissolve the linear poly(MMA‐MAA) core to form the poly(NIPAAm‐MAA) hollow latex particles. In the third step, the Fe₃O₄ nanoparticles were generated in the presence of poly(NIPAAm‐MAA) hollow polymer latex particles and formed the poly(NIPAAm‐MAA)/Fe₃O₄ magnetic composite hollow latex particles. The fourth step was to synthesize poly(NIPAAm‐MAA) in the presence of poly(NIPAAm‐MAA)/Fe₃O₄ latex particles to form the poly(NIPAAm‐MAA)/Fe₃O₄/poly(NIPAAm‐MAA) two‐shell magnetic composite hollow latex particles. The effect of various variables such as reactant concentration, monomer ratio, and pH value on the morphology and volume‐phase transition temperature of two‐shell magnetic composite hollow latex particles was studied. Moreover, the latex particles were used as carriers to load with caffeine, and the caffeine‐loading characteristics and caffeine release rate of latex particles were also studied. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2880–2891     

Optimization of the synthesis of poly(octadecyl acrylate) by atom transfer radical polymerization and the preparation of all comblike amphiphilic diblock copolymers

The atom transfer radical polymerization of octadecyl acrylate (ODA) has been investigated and optimized to produce polymers with predetermined molecular weights and narrow polydispersities (<1.2). The poor solubility of the catalytic system formed with conventional ligands such as the N‐(n‐propyl)‐2‐pyridylmethanimine and 2,2′‐bipyridine with Cu(I)Br in nonpolar reaction conditions gave poor control over molecular weight characteristics in ODA polymerizations. The use of N‐(n‐octyl)‐2‐pyridylmethanimine in combination with Cu(I)Br yielded a more soluble catalyst that improved control over the polymerization. The products from the polymerizations were further improved when an initiator, octadecyl 2‐bromo‐2‐methyl‐propanoate, similar in structure to the monomer, was used. Together, these modifications produced polymerizations that showed true controlled character as well as products with predetermined molecular weights and narrow polydispersities. Diblock copolymers of PODA were prepared with methyl methacrylate (MMA) and olig(oethylene glycol) methyl ether methacrylate (OEGMA). The PODA‐block‐POEGMA copolymers are the first examples of all comblike amphiphilic block copolymers. One of PODA‐block‐POEGMA copolymer samples has been shown to self‐assemble as micelles in a dilute aqueous solution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1129–1143, 2005     

Samarium poly(oxamide) polyanions as novel polymeric initiators. One-pot syntheses of graft copolymers

Samarium poly(oxamide) polyanions, formed quantitatively in situ by the reductive coupling polymerization of aromatic diisocyanates with samarium (II) iodide/hexamethylphosphoramide (HMPA) system, were directly used as the polymeric initiators in the graft polymerization with some electrophilic monomers. The graft polymerization of ϵ-caprolactone (CL) with several polyanions derived from bifunctional isocyanates, including tolylene 2,6-diisocyanate, o-tolidine diisocyanate and diphenylmethane diisocyanate, provided the corresponding graft copolymers in one-pot, indicating that the polyanion could work as a new type of reactive polymer. Several factors such as reaction temperature and time and the amount of HMPA and CL affected the behavior of the present polymerization system, and the graft copolymer was obtained quantitatively under the appropriate conditions. The results of the graft polymerizations of tert-butyl methacrylate and methyl methacrylate with the polyanion were also presented. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1381–1387, 1997     

Preparation and phase behavior of poly(4‐trimethylsilylstyrene)‐block‐polyisoprene

Three poly(4‐trimethylsilylstyrene)‐block‐polyisoprenes (TIs), the molecular weights of which were 82,000, 152,000 and 291,000 (TI‐82K, TI‐152K, and TI‐291K), were synthesized by sequential anionic polymerizations. The component polymers were a miscible pair that presented a lower critical solution temperature phase diagram if blended. The TI phase behavior was investigated with transmission electron microscopy. The order–disorder transition could be observed at a temperature between 200 °C (the ordered state) and 150 °C (the disordered state) for the block copolymer TI‐152K. The block copolymer TI‐82K presented the disordered state at 200 °C, whereas TI‐291K was in the ordered state at 150 °C. With the Flory–Huggins interaction parameter between poly(4‐trimethylsilylstyrene) and polyisoprene, which was evaluated by small‐angle neutron scattering for the block copolymers, the TI phase behavior could be reasonably explained by mean‐field theory. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1214–1219, 2005     

Poly[(sodium sulfamate/carboxylate)isoprene‐b‐2‐vinyl pyridine] block polyampholytes: Synthesis and self‐assembly in aqueous media

We report on the synthesis of poly[(sodium sulfamate/carboxylate) isoprene‐b‐2‐vinyl pyridine] block polyampholytes (SCPI‐P2VP), utilizing anionic polymerization and post polymerization functionalization reactions. The precursor poly(isoprene‐b‐(2‐vinylpyridine)) diblock copolymers (PI‐P2VP), containing a polyisoprene (PI) block with high 1,4 microstructure, were prepared by anionic polymerization high vacuum techniques, in two steps, involving change of the polymerization solvent. Subsequent functionalization of the PI block with chlorosulfonyl isocyanate, introduced sulfamate and carboxylate groups in the polymer chains and produced the desired block polyampholytes. The successful synthesis of the polyampolytes was corroborated by elemental analysis and IR spectroscopy measurements. The self‐assembly behaviour of the aforementioned polyampholytes was studied in aqueous solutions as a function of pH, by aid of dynamic and static light scattering, zeta potential, fluorescence spectroscopy and atomic force microscopy. Experimental results indicate that the block polyampholytes form micellar structures with P2VP cores and SCPI coronas at pH > 6, whereas more compact nanoparticles are formed at pH < 4 from the complexation of positively charged P2VP and SCPI, stabilized by excess negative charges of uncomplexed SCI segments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characteristics of poly(N‐isopropylacrylamide‐co‐methacrylic acid)/Fe3O4 thermosensitive magnetic composite hollow latex particles

In this study, the poly(NIPAAm–MAA)/Fe₃O₄ hollow latex particles were synthesized by three steps. The first step was to synthesize the poly(methyl methacrylate‐co‐methylacrylate acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first step, the second step was to polymerize N‐isopropylacrylamide (NIPAAm), MAA, and crosslinking agent (N,N'‐methylene‐bisacrylamide (MBA)) in the presence of poly(MMA‐MAA) latex particles to form the linear poly(MMA‐MAA)/crosslinking poly (NIPAAm‐MAA) core‐shell latex particles. After the previous processes, the core‐shell latex particles were heated in the presence of NH₄OH to dissolve the linear poly(MMA‐MAA) core in order to form the poly(NIPAAm‐MAA) hollow latex particles. In the third step, Fe²⁺ and Fe³⁺ ions were introduced to bond with the ? COOH groups of MAA segments in the poly(NIPAAm‐MAA) hollow polymer latex particles. Further by a reaction with NH₄OH and then Fe₃O₄ nanoparticles were generated in situ and the poly(NIPAAm‐MAA)/Fe₃O₄ magnetic composite hollow latex particles were formed. The concentrations of MAA, crosslinking agent (N,N'‐methylene bisacrylamide), and Fe₃O₄ nanoparticles were important factors to influence the morphology of hollow latex particles and lower critical solution temperature of poly(NIPAAm–MAA)/Fe₃O₄ magnetic composite hollow latex particles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012